Traction vehicles are commercially available for the moving of rail cars. Since a loaded rail car may be much heavier than the traction vehicle, means are provided as described, for transferring some of the weight of the railway car to the traction vehicle to provide a sufficient amount of traction to the pulling vehicle so that it can move the rail car without slippage of the wheels on the track. See, for example, U.S. Pat. Nos. 2,718,195; 3,420,191; 3,540,381; 3,232,241; and 3,892,187.
Furthermore, the traction vehicles carry retractable road wheels so that the vehicle can climb onto a railroad track, and then retract its road wheels to operate as a rail vehicle, and alternatively to lower its road wheels to permit it to leave the track and move about the yard to another track, or into a storage shed or the like.
Accordingly, this versatile vehicle can be relatively small and be powered by gasoline or diesel engine, while being capable of replacing an entire switch engine, having the added versatility of being able to operate off of the tracks as well as on the tracks.
The retractable wheeled vehicles of the prior art have exhibited certain disadvantages. One of these disadvantages is that the road wheels, being generally retractable by hydraulic cylinders, are not spring mounted in the usual manner of road wheels of a large vehicle, so that the vehicle is subject to considerable shock as it moves across rough terrain.
Furthermore, the sudden derailment of the vehicles is a fairly common circumstance, as the vehicles are climbing on or off of the rails in their accustomed manner. In many designs of the retractable wheel rail car moving vehicle, a sudden derailment can cause the rails to slam against the brake drums of the rail wheels, with the likely result of damage and loss of brake action.
Also, the center pivot-type couplers which are conventionally utilized provide the capability for lateral movement, to accommodate turning of the vehicle while under an extremely heavy load imposed by the weight transfer system which is customarily utilized to transfer weight from the rail car to the traction vehicle. Accordingly, as the coupler means does pivot under this heavy weight, granular material such as sand or the like can scour the moving surfaces, causing accelerated wear and other damage to the coupler.
In accordance with this invention, technical solutions to the above problems, as well as other advantages, are provided in an improved, retractable wheeled vehicle, which is typically contemplated for use as a rail car moving traction vehicle having the capability of operating both on and off railroad tracks.